As illustrated in FIGS. 1-3, the exterior bottom surface of a human foot comprises, from front to back: five toes 1, toe mounds 2, the longitudinal medial (inner) arch 3, the longitudinal lateral (outer) arch 4, and the heel 5. As illustrated in FIGS. 4 and 5, internally, the toes 1 are formed from the phalanges 12; the toes mounds 2 are formed from the first to fifth metatarsal bones 13; the medial arch 3 is formed by the calcaneus 14, the talus 15, the navicular 16, the three cuneiforms 17, and the first, second, and third metatarsals 13; the lateral arch 4 is formed by the calcaneus 14, the cuboid, and the fourth and fifth metatarsals 13; and the heel 5 is formed from the calcaneus 14. The metatarsophalangeal joints (MTP) 18 are the joints where the metatarsals meet the phalanges 12.
The term medial refers to the part of the body closest to the midline of the body. The medial arch 3 refers to the high arch between the inner portion of the heel 5 and the first, or big, toe. The term lateral refers to the part of the body along the outside of the body. The term lateral arch 4 refers to the low arch between the outer portion of the heel 5 and fifth, or pinky, toe.
The MTP joints 18 are hinge joints in the foot. Each metatarsal bone 13 has a different degree of hinge from its respective phalange 12 (toe) when the foot is in a neutral position. The first metatarsal has the highest degree of hinge from the first toe. The fifth metatarsal has the lowest degree of hinge from the fifth toe. As illustrated in FIG. 4, the angle A from the first MTP to the navicular bone 16 (highest point of medial arch) is approximately twenty degrees. As illustrated in FIG. 5, the angle A from the fifth MTP 18 to the base of the fifth metatarsal 13 is less than five degrees.
As illustrated in FIG. 4, the medial arch has multiple angles: The acute angle A from the first MTP 18 to the navicular bone 16 and calcaneus 14, the obtuse angle B from the Navicular bone 16 to the first MTP 18 and calcaneus 14, and the acute angle C from the calcaneus 14 to the Navicular bone 16 and MTP 18.
As illustrated in FIG. 2-7, the foot contains many different types of natural movements. Dorsiflexion and plantar flexion refers to extension or flexion of the foot at the ankle 7. Dorsiflexion 6 is the movement upwards towards the body, where the toes 1 are brought closer to the shin 8. This decreases the angle between the dorsum 9, or upper surface, of the foot and the leg. Plantar flexion is the movement downwards away from the body, which decreases the angle between the sole 10, or bottom surface, of the foot and the back of the leg. The terms forefoot extension and forefoot flexion may be used interchangeably with the forefoot being plantar flexed (plantar flexion=forefoot extension) and dorsi flexed (dorsiflexion=forefoot flexion). As illustrated in FIGS. 6 and 7, when the forefoot 11 is in a position of extension, the forefoot 11 hinges towards the body at the MTP joints 18, and everted in relation to the heel 5/calcaneus 14. As illustrated in FIGS. 4-5, when the forefoot 11 is in a neutral flexion position, the forefoot 11 is un-hinged at the MTP joints 18 and is neutral in relation to the heel 5/calcaneus 14. When the forefoot 11 is in a position of full flexion, the forefoot 11 hinges down away from the body at the MTP joints 18, and inverted in relation to the heel 5/calcaneus 14.
Eversion is the movement of any part of the foot away from the median, or midsagittal, plane. Inversion is the movement of any part of the foot towards the median plane. Eversion and inversion can refer to the forefoot 11, heel 5, and subtalar joint. The subtalar joint (STJ) is the joint at the meeting of the calcaneus 14 and the talus bone 15. The subtalar joint is used to measure the overall angle of the foot in the medical field.
The terms everted and inverted refer to the forefoot 11 and heel 5 positions at a particular point in time, and used in relation from the forefoot 11 to the heel 5. The term everts is used to describe the action of eversion. The term inverts is used to describe the action of inversion.
As illustrated in FIGS. 4-15, movements of the foot are involved in the natural human gait, which is the pattern of movement of the feet during walking or running over a solid surface/ground 19. The human foot acts as a tripod during a normal gait. As illustrated in FIG. 8, there are three points of contact on the bottom surface of the foot as it touches the ground during a normal gait: the first metatarsal point of contact 20, the fifth metatarsal point of contact 21, and the heel point of contact 22. These three points of contact act as a tripod of support.
The heel 5 and subtalar joint maintain similar actions of eversion and inversion throughout a natural human gait pattern. The heel 5 and forefoot 11 have opposite actions of eversion and inversion throughout a natural human gait pattern.
Research has proven that when the forefoot 11 is everting, it directly correlates with the heel 5 inverting. This motion is known as “supination.” The same is true of the opposite actions: when the forefoot 11 is inverting, the heel 5 is everting during weight bearing. This motion is known as “pronation.” Pronation (eversion) and supination (inversion) refer to the rotation of the foot at the subtalar joint.
The forefoot's actions of eversion and inversion control the action of the heel's inversion and eversion. The forefoot's actions therefore determine the foot's tripod, and the rate of pronation and supination.
The terms varus and valgus are interchangeable with the terms inverted and everted. The terms varus and valgus are typically used to describe the angle of the forefoot 11 and heel 5 in non-weight bearing positions. A forefoot varus position is the inward angulation (inverted) of the forefoot 11 in relation to the subtalar joint and the ground 19. A forefoot valgus position is the outward angulation (everted) of the forefoot 11 in relation to the subtalar joint and the ground 19.
As illustrated in FIGS. 6-7, in non-weight bearing position of the foot, when the forefoot 11 is in extension (plantar flexion of the metatarsophalangeal joints 18 (MTP's), the hinge angle is up to 45 degrees As the forefoot 11 flexes to absorb ground 19 contact, the MTP joints 18 un-hinge. This decreases angles D and E to zero. Angles A and C decrease slightly, and the medial arch 3 is lowered a proper amount to absorb force. As illustrated in FIG. 4, Angle A from the first MTP joint 18 to the Navicular bone 16 and the heel 5/calcaneus 14 determines the height of a person's longitudinal medial arch 3. This angle A varies between approximately 20 and 15 degrees during a normal gait pattern. This allows the medial arch 3 to contract and reach a normal height. As this angle A decreases, Angle C also decreases, and Angle B increases towards 180 degrees. As this occurs, the length between Angles A and C, the longitudinal medial arch 13, increases. As the longitudinal medial arch 13 increases in length, the forefoot's 11 angle of inversion in relation to the heel 5 also increases.
This poor foot position of inverted forefoot, everted heel, and lowered and lengthened medial arch is commonly known as “medial arch collapse” or “flat feet.”
There are two main types of gait patterns in a normal foot (a foot without a structural deformity): a proper gait pattern, and a gait pattern with hyper-pronation at the subtalar joint, more commonly known as “over pronation.”
A proper gait pattern occurs when the foot experiences a normal, healthy amount of pronation and supination. Depending on the pace of walking, jogging, or running, either the forefoot or heel may be the first point of ground contact in proper gait pattern. In all paces, the heel 5 leaves the ground prior to the forefoot 11, and the toes 1 are the last point of contact to leave the ground 19. In proper gait pattern, the forefoot 11 will be used in controlling the pronation and supination. In proper gait pattern, the forefoot 11 remains on the same plane as the ground 19. Due to the fact that the forefoot 11 remains on the same plane as the ground 19, it gives the appearance that the rearfoot is causing the changes in inversion, eversion, and hinging. In reality, the forces of the forefoot 11 against the ground 19 cause the changes in angles at the MTP's 18 that move the heel 5 and lower leg. Prior to initial ground contact, the forefoot 11 begins in moderate extension, and is moderately hinged and everted in relation to the heel 5. The forefoot 11 goes through flexion by un-hinging, and inversion as a mechanism to absorb ground contact, and stops un-hinging and inverting when it arrives at the same plane as the heel 5. Angles D and E decrease to zero. Angles A and C decrease slightly (less than 5 degrees of change). The forefoot 11 then begins extension by re-hinging and eversion again as a mechanism to push off of the ground 19. Angle D increases at a slightly higher rate than Angle E, causing the heel 5 to be slightly inverted upon push off. Angles A and C increase to their original angles.
From a rear point of view, the heel 5 begins slightly inverted, everts to a neutral position, and then lifts off the ground and inverts moderately as the forefoot 11 pushes off the ground 19. In a proper gait pattern, the forefoot 11 does not become inverted in relation to the heel 5. Therefore, the heel 5 is never everted in relation to the ground. The heel 5 is inverted in non-weight bearing position before and after ground contact, and neutral during weight bearing position. Because the heel 5 is non-weight bearing while inverted, it remains in line with the lower leg. This position is not susceptible to injury, and allows the hips to externally rotate and extend. External hip rotation and hip extension both allow the gluteus muscles to contract.
As illustrated in FIGS. 4-15, a normal, healthy human gait pattern, the proper foot posture is:                1) An initial foot contact having (FIG. 12):                    a) First metatarsophalangeal joint 18 in a moderately plantar-flexed (hinged) position, Angles D and E approximately 15-25 degrees. Angles A and C approximately 20 degrees            b) Forefoot 11 in an everted angle in relation to the heel 5, and is parallel with the ground 19;            c) The subtalar joint and heel 5 are inverted to both the ground 19 and the forefoot 11 prior to ground contact.            d) The heel 5 strikes the ground 19 on the outer (lateral) half due to the inverted position.                        2) A loading response having:                    a) Forefoot 11 contacts and absorbs the ground 19, and inverts to a neutral angle in relation to the heel 5.            b) The MTP's 18 un-hinge: Angles D and E decrease to zero. Angles A and C decrease slightly and remain above 15 degrees.            c) The heel 5 everts to a neutral position.            d) The forefoot 11 and heel 5 actions place the foot in a motion of “pronation.”                        3) A mid-stance having (FIGS. 14-15):                    a) The forefoot 11 in a neutral angle in relation to the heel 5.            b) The toes 1 contact and push against the ground 19 for stabilization.            c) The forefoot 11 and heel 5 are both firmly on the ground 19, and on the same plane as the ground (Angles D and E at 0 degrees)            d) The foot's motion of pronation begins to transition to supination.                        4) A terminal stance having:                    a) Forefoot re-extends by hinging at the MTP's 18. Angles D and E increase up to 45 degrees. Angle D is slightly greater than Angle E, causing:            b) Forefoot 11 eversion to a greater degree of everted position in relation to the heel 5 than the initial contact position, to allow for greater foot push off.            c) The heel 5 lifting off the ground and inverting in relation to the forefoot 11 and ground 19.            d) The forefoot 11 and heel 5 actions place the foot in a motion of “supination.”                        5) A toe off push off position having (FIG. 12-13):                    a) The forefoot 11 and toes 1 pushing off of the ground 19 from an everted position, and on the same plane as the ground 19.            b) The inverted position of the heel 5 allows the hips to extend and externally rotate. This places the body in a healthy position through swing phase.                        
As illustrated in FIGS. 16-21, in an improper gait pattern of “over pronation”, the forefoot 11 begins slightly extended, with the MTP's 18 slightly hinged and in a neutral or slightly everted position in relation to the heel 5. As the forefoot 11 absorbs ground contact, Angles D and E decrease to 0. Due to inefficient ground absorption, the first MTP 18 continues to un-hinge, causing Angles A and C to decrease significantly. Therefore, the forefoot 11 inverts past a neutral relationship to the heel 5, to a moderately inverted position and the medial arch 3 lengthens and lowers. The forefoot 11 then extends by re-hinging and everts to push off of the ground 19 from a neutral or slightly everted position.
From a rear point of view, the heel 5 begins in a neutral or slightly inverted position. The heel 5 everts to a moderately everted position, and then lifts off the ground 19 in a neutral or slightly inverted position. This places the forefoot 11 in an inverted position and the heel 5 in an everted position during a weight bearing position. Research has proven that an everted heel 5 position during a weight bearing position leads to instability of the foot and leg, and soft tissue injury. The repeated inverted position of the forefoot 11 during a weight bearing position may lead to the soft tissue foot deformity of “forefoot varus.”
A varus deformity is the inward angulation of the distal segment of a foot bone in relation to the subtalar joint and ground. A valgus deformity is the opposite, an outward angulation of the distal segment of a foot bone in relation to the subtalar joint. The terms varus and valgus always refer to the direction that the distal segment of the joint points, and are primarily used to describe the angle of the forefoot 11 or heel 5 in a non-weight bearing position.
In a forefoot varus deformity of the foot, also called forefoot supinatus, the first metatarsal 13 angles inward over time due to flexible soft tissue deformity of the foot. Forefoot varus deformity begins with excessive forefoot inversion in the gait pattern. During the loading response and mid-stance positions of an “over pronation” gait pattern, the forefoot 11 is pushed into an inverted (varus) angle in relation to the heel 5. As the forefoot 11 varus condition worsens, the forefoot 11 remains in an inverted position while in a non-weight bearing position. This causes the medial arch 3 to lengthen and have a lower height, and the foot appears to be “flat” during non-weight bearing positions. As illustrated in FIG. 21, this position forms an unstable tripod support due to the everted heel 5 position throughout the gait pattern. At this point, the gait is severely affected as during the initial contact, loading response, mid-stance, terminal stance, and toe push off positions, as the forefoot 11 remains in an inverted (varus) angle in relation to the heel 5. A non-weight bearing forefoot varus of 0 to 4 degrees is considered normal and healthy. A non-weight bearing forefoot varus of 8 degrees or greater has proven to lead to instability and soft tissue injury in the foot and leg.
Forefoot varus causes the bones on the inside edge of the forefoot 11 to sit higher off the ground surface 19 than the outside of the foot during non-weight bearing positions. Thus, in theory (without gravity), only two points of the foot would contact the ground surface: the heel point of contact 22 and the fifth metatarsal point of contact 21. However, in reality, when the foot contacts the ground, there must be a third point, the first metatarsal point of contact 20, in order to balance a person's weight.
There are two ways for a person with forefoot varus to complete the three points 20, 21, and 22 of ground contact. The first way, as what happens in pre-existing shoes, is that the forefoot 11 remains in an inverted relation to the heel 5. Therefore, the entire foot must rotate to the inside in order to contact the ground with three points 20, 21, and 22. In this position, the lateral aspect of the foot does not have the proper amount of weight bearing, the forefoot 11 (first metatarsophalangeal joint in particular) is not extended, and the heel is everted 5. Forefoot varus leads to lengthening the medial arch 3 of the foot, leading to a lower height, and even eventual flattening of this medial arch 3. The combination of an everted heel 5 and an un-extended, inverted forefoot 11 is poor foot positioning. It makes the foot, ankle, and body as a whole susceptible to injury. The everted position of the heel 5 during weight bearing positions lowers the medial arch 3 height excessively, which negatively changes a person's gait pattern, leading to several injuries. The forefoot varus foot type may lead to the following injuries: plantar fasciitis, iliotibial (IT) band syndrome, ACL injuries, medial knee injuries, and Achilles tendonitis. The foot position can also create atrophy in certain muscles, notably the gluteus maximus, gluteus medius, and gastrocnemius. The gluteus muscles are unable to contract due to lack of hip extension and external rotation.
In summary, a foot with a normal forefoot 11 and heel 5 relationship may have a poor “over pronation” gait pattern in which the forefoot 11 is inverted in relation to the heel 5 during weight bearing positions, particularly during the mid-stance. This poor gait pattern leads to injuries, as well as the soft tissue deformity of “forefoot varus.” In a forefoot varus foot, the forefoot 11 is inverted in relation to the heel 5 prior to ground contact. Therefore, the everted heel 5 and medial arch 3 height collapse occurs throughout the gait pattern and is more severe. This makes a forefoot varus foot type highly susceptible to the injuries previously listed.
As illustrated in FIGS. 14-19, a foot with a neutral forefoot 11 and heel 5 relationship with an improper gait pattern may “over pronate” due to poor footwear and several other factors. The following gait pattern occurs:                1) An initial foot contact having (FIG. 14):                    a) First metatarsophalangeal joint 18 in a slightly plantar flexed (hinged) position, Angles D and E approximately 15-25 degrees. Angles A and C approximately 20 degrees.            b) Forefoot 11 in a slightly everted angle, or neutral, in relation to the heel 5, and slightly inverted in relation to the ground 19.            c) The subtalar joint and heel 5 are slightly inverted, or neutral, in relation to the forefoot 11, and slightly inverted in relation to the ground 19.            d) Heel 5 strikes the ground 19 on the outer (lateral) half due to the slightly inverted position.                        2) A loading response having:                    a) The forefoot 11 contacts and absorbs the ground 19, and inverts past a neutral position to a slightly inverted position in relation to the heel 5, due to instability.            b) The MTP's 18 unhinge. The first MTP 18 unhinges excessively. Angles D and E decrease to 0. Angles A and C decrease excessively to under 10 degrees.            c) The heel 5 everts past a neutral position to slightly everted position in relation to the forefoot 11 and ground 19.            d) The forefoot 11 and heel 5 actions place the foot in a motion of “over pronation.”                        3) A mid-stance having (FIGS. 18-19):                    a) The forefoot 11 in an inverted angle in relation to the heel 5; the heel 5 in an everted angle while weight bearing.            b) The toes 1 do not properly push against the ground 19, losing stability.            c) The forefoot 11 and heel 5 are both on the ground, but without stability. Angles A and C are between 10 and 0 degrees.            d) The position of inverted forefoot 11 and everted heel 5 lowers and lengthens the medial arch 3, and places the body at a position that is moderately susceptible to injury. In some cases, this repeated position leads to the soft tissue deformity of forefoot varus.                        4) A terminal stance having:                    a) Forefoot re-extends by hinging at the MTP's 18. Angles D and E increase moderately, to less than 45 degrees. Angles A and C return to approximately 15 degrees.            b) Forefoot 11 everts to a slight degree of everted position in relation to the heel 5.            c) The heel 5 lifting off the ground 19 and inverts to a position of slightly inverted in relation to the forefoot 11 and ground 19.            d) The forefoot 11 and heel 5 actions place the foot is in a motion of “supination”.                        5) A toe push off position having:                    a) The forefoot 11 pushing off of the ground 19 from a slightly everted position, and on the same plane as the ground 19.            b) The slightly inverted position of the heel 5 allows the hips to slightly extend and externally rotate.                        
As illustrated in FIGS. 18-21, an “over pronation” gait pattern may lead to the soft tissue foot deformity of “forefoot varus.” A foot with a soft tissue deformity of forefoot varus in non-weight bearing positions has an improper gait pattern that is highly susceptible to injury:                1) An initial foot contact having (FIG. 18):                    a) First metatarsophalangeal joint 18 in a neutral position, the MTP joints 18 are already un-hinged. Angles D and E are less than 15 degrees. Angles A and C are less than 10 degrees            b) Forefoot 11 in an inverted angle (“varus”) in relation to the heel 5.            c) The subtalar joint and heel 5 are everted in relation to the forefoot 11 prior to ground contact.            d) The heel 5 strikes the ground on the inner (medial) half due to the everted position.                        2) A loading response having:                    a) The forefoot 11 contacts and inefficiently absorbs the ground 19, and inverts excessively.            b) The MTP's 18 unhinge. The first MTP 18 unhinges excessively. Angles D and E decrease to 0. Angles A and C decrease to 0 degrees.            c) The heel everts excessively.            d) The forefoot 11 and heel 5 actions place the foot in a motion of extreme “over pronation.”                        3) A mid-stance having (FIG. 19):                    a) The forefoot 11 in a position of extremely inverted in relation to the heel 5.            b) The toes 1 do not absorb the ground 19 or add any stabilization to the foot.            c) The heel 5 in a position of extremely everted in relation to the forefoot 11 and the ground. Angles A and C are at 0 degrees, and the medial arch 3 lengthens and lowers to the ground 19.            d) The foot's motion of extreme over pronation flattens the height of the medial arch 3 and places the foot and body in a position that is unstable and highly susceptible to injury.                        4) A terminal stance having:                    a) Forefoot re-extends by hinging at the MTP's 18. Angles D and E increase slightly, to approximately 15 degrees. Angles A and C return to under 10 degrees.            b) Forefoot 11 is not able to evert back to neutral, and is in a position of slightly inverted in relation to the heel 5.            c) The heel 5 does not lift off the ground 19, is not able to invert to neutral, and is in a position of slightly everted in relation to the forefoot 11 and the ground.            d) The forefoot 11 and heel 5 actions do not allow the foot to properly supinate.                        5) A toe push off position having:                    a) The foot pushing off the ground 19 all at once in an inefficient and injury susceptible position.            b) The everted position of the heel 5 forces the hips to flex and internally rotate during the swing phase, making the leg susceptible to further injury.                        
The current structure of most commercially available shoes increases the progression and angle of forefoot varus by restricting the forefoot 11. Most shoes force a person into an “over pronation” gait pattern rather than a proper gait pattern. The over pronation gait pattern leads to forefoot varus in a percentage of people with a neutral foot, and increases the angle of inverted (varus) forefoot in people who have already developed forefoot varus.
There are two main components of shoe manufacturing. The first component is the last. A last is a mechanical form that has a shape similar to that of a human foot. It is used by shoemakers in the manufacture and repair of shoes. A last is made of high density plastic, and is designed to give the shoe its desired shape. Both the “upper” and the sole are attached to the last in the manufacturing process. The last determines aspects such as the general shape, forefoot width, heel height, and toe spring. The second main component is the outsole mold. The mold is based off of technical engineering drawings of the outsole. The mold determines aspects such as the thickness of the outsole, the contour, and the depth of flex grooves. The toe spring in most commercial running shoes is created with a small toe spring in the last, combined with tapering of outsole towards the toe. The tapering is designed so that the thickness of the outsole is less at the tip of the toe than it is under the MTP joints. This design allows the foot to roll forward and off the toe when walking or running. In the manufacturing of most commercial shoes, the mold is created to match the contour of the last. For example, a last with a ten degree toe spring will have an outsole with a 10 degree toe spring,
In most shoes, the forefoot 11 and heel 5 are on the same plane. This does not allow the forefoot 11 to extend and create an everted plane in relation to the heel 5. Because the forefoot 11 must invert as a mechanism to absorb contact (pronation), the forefoot 11 inverts from a neutral position to an inverted position inside the shoe. This causes the heel 5 to begin in neutral and evert to an everted position inside the shoe, lowering the medial arch 3 excessively.
In most running shoes, the forefoot is gradually contoured from the rearfoot to raise up approximately 15 degrees in the forefoot. In some running shoes, the forefoot contains flex grooves, designed to allow the forefoot to hinge from the rearfoot This hinge is known as “toe spring.” In these shoes, flex grooves are closed in non-weight bearing positions of the shoe. The flex grooves open with external pressure, but are difficult to open with the internal pressure of the foot. Thus, previous shoes with flex grooves do not allow the forefoot to extend fully (hinge and evert) prior to initial contact. Further, when the flex grooves are closed, the sole still contours to force the forefoot up in a slight hinge of approximately 15 degrees. Thus, previous shoes with flex grooves do not allow the forefoot to un-hinge to zero degrees with the internal pressure of the foot, as in mid stance and static standing. Overall, most running shoes encourage the foot to remain in a slightly extended position throughout gait pattern. The inadequate ability of the running shoe to get to an unhinged mid stance position causes instability in the loading response and mid stance that may lead to an “over pronation” gait pattern.
In some models of basketball, cross training, dance, minimal, and other athletic shoes, the sole is significantly flatter compared to running shoes, and contours the forefoot up from the rearfoot at approximately five degrees. This allows the foot to obtain an un-hinged accurate mid stance and static standing foot position. The shoe is able to be hinged with external pressure, but not with the internal pressure of the foot. Therefore, these shoes do not allow the forefoot to extend (hinge and evert) in non-weight bearing. Thus, these shoes do not allow the proper foot position of moderately extended (hinged and everted) forefoot prior to initial contact, and restricts the foot from fully re-extending in terminal stance. This causes instability during initial contact and loading response that leads to poor foot posture during mid stance and an “over pronation” gait pattern, and does not allow for a proper push off.
In most shoes, the outsole heel is flat and parallel with the ground surface. This encourages the foot to contact the ground surface all at once in a neutral position. Due to natural forefoot inversion and heel eversion during loading response, a neutral starting point in gait pattern leads to an inverted forefoot and everted heel position during loading response and mid stance.
Many commercially available shoes disclose a “heel to toe drop” which there is more cushion in the heel than in the forefoot, and toe boxes, which are raised off of the ground to simulate the position of toe push off in terminal stance. The toes are an important part of foot stabilization during mid stance, but are not allowed to contact the ground during mid stance in most shoes. The combination of the heel to toe drop and the toes not engaged with the ground places the body's weight excessively onto a person's heel 5 and midfoot while standing. As stated in the normal gait cycle, when the weight of a person is placed on the forefoot 11, the MTP's un-hinge to absorb the ground and the body's weight. Because the heel 5 is higher off the ground than the forefoot, Angles D and E do not decrease to 0, and the forefoot cannot not absorb the proper amount of ground contact. The forefoot attempts to absorb additional ground contact by continuing to un-hinge at the first MTP (Angles A and C decrease). This causes the forefoot to invert excessively, and the medial arch to lengthen and lower. Thus, most shoes encourage the foot to be in an inverted forefoot 11 and everted heel 5 position while standing and during activities.
Most shoes have a wide configuration at the heel and forefoot, but narrow configuration at the midfoot, which does not match the general straight shape of feet from the outside of the heel to the outside of the forefoot. This shoe configuration squeezes in the lateral arch 4 of the midfoot during movement. A person that walks inside a shoe that “squeezes” the outside of their midfoot does not have a natural gait pattern. In shoes with a “squeezed” midfoot, the base of the fifth metatarsal is not allowed to directly push against the ground to add stability. Instead, the foot lands on the heel 5 and is forced to land in the middle of the midfoot, rather than the lateral side of the midfoot. Because of the natural pronation (forefoot inversion heel eversion) during loading response, any instability to the foot during loading response results in over pronation.
Shoes disclosed in the prior art have attempted to correct “over pronation” gait pattern with a wedge on the medial side of the heel and midfoot to assist people making initial contact with their heel inverted rather than everted. The forefoot's actions and proper engagement with the ground control the heel's eversion to a neutral position; therefore, this wedge does not allow a person to properly strengthen their foot; it merely treats the symptoms of poor foot positioning of everted heel and lowered medial arch. Because a person's heel is rounded and the forefoot is allowed to be inverted inside shoes, poor foot positioning can still occur despite a medial wedge designed to prevent everted heel position and medial arch collapse. This design does not address the underlying problem of a forefoot that is not controlling the heel's eversion due to insufficient ground engagement.
Another previously disclosed method to treat over pronation is to create custom orthotics designed to fit inside of shoes. Custom orthotics are generally made of a hard material, and are designed to support the medial arch to keep it from collapsing. Similar to a heel wedge, custom orthotics are designed to prevent the everted position that occurs in the heel and midfoot during mid stance of an over pronation gait pattern. Again, custom orthotics do not allow a person to properly strengthen their foot; it merely treats the symptoms of poor foot positioning at the heel and midfoot. Furthermore, custom orthotics are expensive and time consuming as they must be prescribed, measured, and made to specifications by medical professionals. Even with prescription custom orthotics, a person cannot maintain a natural gait pattern and fully develop their muscles. This is due to the fact that the base of the first metatarsal, cuneiform bones, and navicular bones are not designed to be weight bearing. These bones pushing down against a hard orthotic may cause deformity that leads to forefoot varus. In addition, the medial arch naturally raises and lowers during gait pattern. A custom orthotic attempts to keep the medial arch at a fixed percentage throughout gait pattern. Stress on joints will continue to occur if the orthotic is placed into an improper shoe.
Prior art designed to correct forefoot varus is to place a wedge under medial side of the forefoot. This design “brings the ground up to the forefoot varus” rather than allowing the forefoot varus to rotate to the ground. This design has not been widely implemented in shoes or orthotic design. The problem with this design is that forefoot varus is an acquired soft tissue deformity, not a bone structure deformity (except in rare cases). A medial forefoot wedge restricts the forefoot from extending and everting, and therefore does not allow a natural and proper gait pattern. The pressure from this wedge under the first metatarsophalangeal joint may further invert the forefoot and cause a higher degree of forefoot varus.
Pre-existing minimal-style barefoot running shoes have attempted to create a more natural gait pattern, but do not compensate for the condition of forefoot varus. While barefoot running shoes incorporated greater flexibility throughout the shoe, they have not specifically designed the forefoot to extend and evert in relation to the heel. Pre-existing minimal and barefoot running shoes eliminated the “heel to toe drop” of “support” shoes. In doing so, these shoes also eliminated the contour of the foot during non-weight bearing, in which an extended forefoot is on a plane closer to the ground than the heel. This places too much pressure on the metatarsal side of the metatarsophalangeal joints. This pressure may cause the forefoot to flex excessively and invert to relieve the pressure. The flat bottom shape of the minimal shoes therefore causes the foot be in a flat position.
Barefoot activities, such as standing, walking, running, sports, and weight training may allow a person to strengthen certain muscles, take pressure off of certain joints and smaller muscles, and ultimately reduce the amount of “over-use” injuries that occur to the average person. However, many people have poor, unnatural foot positioning during these activities due to a lifetime of poorly designed footwear. This poor foot positioning over a lifetime has created weakness and imbalances in the hips and legs, which can't be easily corrected by engaging in barefoot activities.
Various techniques have been developed to counteract the forefoot varus condition, and the problem of an everted heel in weight bearing. As illustrated in FIG. 22, short foot exercises can treat forefoot varus by shortening 23 the medial side 3 of the foot, thus raising and contracting the medial arch (increasing angles A and C). Further, it changes the forefoot 11 from an inverted position to a neutral position. This allows the heel 5 to change from an everted position to a neutral position. Because the lateral side 4 of the foot is not effected by the short foot exercises, this changes the foot from a position of inverted forefoot and everted heel (over-pronation), and places it in a neutral position.
Accordingly, the subject invention is footwear that substantially mimics barefoot activities, to allow a person to stand, walk, and run naturally as if they were barefoot, and compensates or trains foot muscles to reduce or eliminate the excessive over pronation often seen with forefoot varus.
The subject footwear will permit a person's heel to land naturally during activities. The footwear will permit a person's midfoot to strike along the lateral edge (keeping the medial inner arch off of the ground) during the gait cycle. The footwear will permit the first metatarsophalangeal joint room within the shoe to be extended (plantar flexed, hinged) and forefoot everted in relation to the heel, and allow room in the toe box for less restriction. The toe box will be able to be in full contact with the ground while the rest of the shoe is on the ground as well. The modified shoe is designed to allow for a proper gait pattern by allowing the forefoot to extend and flex, and create both an everted forefoot and neutral forefoot in relation to the heel. The design of the modified shoe will distribute a person's weight across the heel, lateral midfoot, forefoot, and toe box. The footwear will contain a strap emulating a Navicular sling wrap, which will be the shoe's form of medial arch support. The footwear will contain deep pre-stretched flex grooves underneath the MTP joints with a rounded heel and lateral midfoot. The lack of sole material under the medial arch along with the flexibility in the forefoot will allow the extension (hinging and everted plane) of the forefoot that will not force the foot into a singular plane during the gait cycle.